TWIST Gene Mutation in a Patient With RadialAplasia and Craniosynostosis: Further Evidence forHeterogeneity of Baller-Gerold Syndrome

Karen W. Gripp,1* Catherine A. Stolle,2 Livija Celle,1 Donna M. McDonald-McGinn,1Linton A. Whitaker,3 and Elaine H. Zackai1,2

1Division of Human Genetics and Molecular Biology, The Children’s Hospital of Philadelphia,Philadelphia, Pennsylvania

2Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania3Department of Surgery, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania

The term Baller-Gerold syndrome wascoined by Cohen [1979: Birth Defects 15(5B):13–63] to designate the phenotype of cranio-synostosis and radial aplasia. It is thoughtto be a rare autosomal recessive condition,which, in some patients, presents with addi-tional abnormalities, such as polymicrogy-ria, mental retardation or anal atresia. Aphenotypic overlap of Baller-Gerold andRoberts-SC phocomelia syndrome wasnoted when a patient with bicoronal synos-tosis and bilateral radial hypoplasia wasfound to have premature centromere sepa-ration, a finding characteristic of Robertssyndrome [Huson et al.,1990: J Med Genet27:371–375]. Other cases of presumed Baller-Gerold syndrome were rediagnosed as Fan-coni pancytopenia, Rothmund-Thomsonsyndrome or VACTERL association. Thesereports led to a narrowed redefinition ofBaller-Gerold syndrome based on the exclu-sion of cytogenetic and hematopoetic abnor-malities and the absence of additional mal-formations in patients with craniosynosto-sis and preaxial upper limb abnormalities.Here we report on a patient with unilateralradial aplasia and bicoronal synostosiswithout additional malformations and with-out chromosome breakage, who fits this nar-row definition of Baller-Gerold syndrome.We identified a novel TWIST gene mutationin this patient, a Glu181Stop mutation pre-dicting a premature termination of the pro-tein carboxy-terminal to the helix 2 domain.This report provides further evidence that

Baller-Gerold is of heterogeneous cause,and a thorough evaluation is indicated toidentify a possibly more specific diagnosis,including Saethre-Chotzen syndrome. Thisdifferential diagnosis is of particular impor-tance, as it is an autosomal dominant trait.Therefore, the recurrence risk for parentsof an affected child can be 50% if one parentcarries the mutation, as opposed to the 25%recurrence risk for autosomal recessive in-heritance. Offspring of the affected patientalso have a 50% risk to inherit the mutation,while the risk to bear an affected offspringfor an autosomal recessive trait is very low.Am. J. Med. Genet. 82:170–176, 1999.© 1999 Wiley-Liss, Inc.

KEY WORDS: Baller-Gerold syndrome; cra-niosynostosis; radial aplasia;Saethre-Chotzen syndrome;TWIST

INTRODUCTION

Many craniosynostosis syndromes were originallydefined by their clinical presentation. Recently the ge-netic etiology for the most common syndromes wasidentified, such as mutations in the fibroblast growthfactor receptor (FGFR) genes in Pfeiffer, Crouzon, andApert syndromes; and mutations in the TWIST gene inSaethre-Chotzen syndrome [for review see Wilkie,1997]. The craniosynostosis syndrome associated withthe FGFR3 Pro250Arg mutation was defined based onthis specific mutation [Muenke et al., 1997]. Theserelatively common disorders all share an autosomaldominant inheritance pattern. In contrast, Baller-Gerold syndrome is rare, with about 20 reported cases,and it is thought to be autosomal recessive. However,because of the clinical variability in patients with pre-sumed Baller-Gerold syndrome, in some cases leadingto a revised diagnosis of Fanconi anemia [Rossbach et

Contract grant sponsor: Howard Hughes Medical Institute.*Correspondence to: Karen W. Gripp, M.D., Clinical Genetics

Center; Wood Bldg., The Children’s Hospital of Philadelphia,34th St. and Civic Center Blvd., Philadelphia, PA 19104.

Received 8 July 1998; Accepted 30 September 1998

American Journal of Medical Genetics 82:170–176 (1999)

© 1999 Wiley-Liss, Inc.

al., 1996; Farrell et al., 1994], the question has beenraised whether Baller-Gerold syndrome is a distinctentity [Cohen and Toriello, 1996]. Here we report on apatient with findings of craniosynostosis and radialaplasia consistent with the diagnosis of Baller-Geroldsyndrome, in whom we identified a familial mutationin the TWIST gene. We thus add Saethre-Chotzen syn-drome to the list of differential diagnoses in this con-stellation of findings, and report the first case at riskfor autosomal dominant inheritance.

CLINICAL REPORT

This girl was the first child born to nonconsanguin-eous parents. There was no prenatal exposure to medi-cations or alcohol throughout the pregnancy. She wasborn at term by spontaneous vaginal delivery with abirth weight of 3 kg. Left radial aplasia and a floatingthumb were noted, and she reportedly had a prominentforehead with unusual skull shape. A large occipitalossification defect was present. Reconstructive surgeryof her left hand performed during infancy included am-putation of the floating thumb and index finger polli-cization. At 3 9/12 years she developed increased intra-cerebral pressure due to bicoronal synostosis (Fig. 1),and a bifrontal craniectomy in combination with recon-structive surgery for orbital hypertelorism and zygo-matic hypoplasia was performed. At 6 years the persis-

tent ossification defect of the occiput was covered withan implant. Multiple cranial reconstructive procedureswere performed thereafter, including forehead andmidface advancement, reshaping of the nose and stra-bismus correction. She has not had other medical prob-lems and finished high school without difficulties. At25 years she presented for prenatal counseling in herfirst pregnancy. Physical examination at this timeshowed a height of 166 cm (50–75th centile), and anOFC of 52 cm (2nd centile). There was mild epicanthus,ptosis was not present, ears were of normal shape andposition with normal crus (Fig. 2). The right arm was ofnormal size and proportions and had full range of mo-tion. The right thumb was not broad or deviated, andthere was no syndactyly (Fig. 3). Both feet showed mildhallux valgus.

Family members were examined after a mutationwas identified in the patient. Her father reported ahistory of moderate hearing loss since age 5 years anddiabetes mellitus type II. He had had no surgeries. Hisheight was 177 cm (50–75th centile), OFC 58 cm (<98thcentile). Facial asymmetry (Fig. 4), a high and narrowpalate, slightly broad thumbs and bilateral hallux val-gus (Fig. 5) were noted and there was no syndactyly.The patient’s mother was 178 cm tall (>98th centile),and OFC was 57 cm (50–98th centile). Physical exami-nation was unremarkable. The patient’s brother had noreported medical problems and physical findings were

Fig. 1. Preoperative photographs of the patient at age 3 9/12 years, showing hypertelorism, increased biparietal distance and midfacial hypoplasia.

TWIST Gene Mutation in Baller-Gerold Syndrome 171

unremarkable except for mild brachycephaly. He hasone healthy 2-year-old son, whose physical status wasnormal. The patient’s 15-year-old sister has a history ofaqueductal stenosis diagnosed at 14 years and repairedsurgically. Height was 178 cm (>98th centile) and OFC59 cm (>98th centile). Facial asymmetry, proptosis, aprominent nose, maxillary hypoplasia with a shortphiltrum, a high palate and an apparently posteriorlyangulated right ear were noted (Fig. 6). She had nor-

mal thumbs, mild hallux valgus bilaterally and no syn-dactyly (Fig. 5). The patient’s youngest sister was 11years old and in good health. Physical status was un-remarkable.

LABORATORY EVALUATIONThe patient’s chromosome breakage study induced

with diepoxybutane had a normal result; thus there isno laboratory evidence for Fanconi anemia.

Fig. 3. Left: The patient’s upper limbs at age 25 years, showing no abnormality of the right hand and status after index finger pollicization of the leftarm with radial aplasia. Right: The patient’s feet with mild hallux valgus bilaterally.

Fig. 2. The patient at age 25 years, showing facial asymmetry, mild epicanthus, downslanting palpebral fissures and midfacial hypoplasia.

172 Gripp et al.

Fig. 4. The patient’s father showing facial asymmetry and a flat occiput.

Fig. 5. Left: The patient’s father’s feet with bilateral hallux valgus. Right: The patient’s sister’s feet with bilateral mild hallux valgus.

TWIST Gene Mutation in Baller-Gerold Syndrome 173

Mutational analysis of the TWIST gene was per-formed after DNA extraction using a commerciallyavailable kit (Gentra Systems, Inc., Minneapolis, MN)according to manufacturer’s instructions. Amplifica-tion was performed by polymerase chain reaction, us-ing standard conditions and primers specific for theTWIST gene [Howard et al., 1997]. DNA sequencingwas performed using a cycle sequencing kit with dye-labeled terminators (PE Applied Biosystems, Inc., Fos-ter City, CA) according to manufacturer’s instructions.Sequence analysis was performed on an ABI 377 auto-mated DNA sequencer. The mutation was confirmed bysequencing both DNA strands. The patient was foundto be heterozygous for a G to T base change at nucleo-tide 541, predicting a change in the codon for glutamicacid (CAG) to a stop codon (TAG) at position 181. Thepatient’s father and the older sister were found to carrythe mutation. Her mother, brother and the youngestsister do not have the mutation. The mutation was notpresent in 160 control alleles examined by conforma-tion sensitive gel electrophoresis [Ganguly et al., 1993].

DISCUSSION

Our patient presented with radial aplasia and cra-niosynostosis, findings characteristic for Baller-Geroldsyndrome. Baller [1950] reported on a 26-year-oldwoman with craniosynostosis, right aplasia and left hy-poplasia of the radii, born to third cousins twice re-moved. Gerold [1959] saw a 16-year-old boy with tur-ricephaly and absent radii and thumbs. The patient’ssister was born with similar malformations and diedduring infancy. Since then other case reports have ex-tended the diagnosis of Baller-Gerold syndrome to in-

clude multiple additional anomalies, such as analanomalies including imperforate anus or anteriorly po-sitioned anus [Greitzer et al., 1974; Feingold et al.,1979; Anyane-Yeboa et al., 1980; Boudreaux et al.,1990; Dallapiccola et al., 1992; van Maldergem et al.,1992; Lin et al., 1993], cardiac anomalies includingventricular septum defect and tetralogy of Fallot [Gre-itzer et al., 1974; Lin et al., 1993], and CNS abnormali-ties, such as polymicrogyria, hydrocephalus, agenesisof the corpus callosum or seizure disorders [Greitzer etal., 1974; Feingold et al., 1979; Pelias et al., 1981; Bou-dreaux et al., 1990; Dallapiccola et al., 1992; Dunac etal., 1995]. Of particular interest to the delineation ofBaller-Gerold syndrome are numerous reports showingoverlap with other congenital malformation syndromesand an association. Huson et al. [1990] described a 26-year-old woman with bicoronal synostosis and bilateralradial hypoplasia with short thumbs. Because of hershort stature, a skeletal survey was performed showingbilateral coxa valga and hypoplastic fibulae. These ad-ditional radiographic findings led to suspicion of Rob-erts-SC phocomelia syndrome, which was confirmed bypremature centromere separation on cytogeneticanalysis. Other authors reported patients diagnosedwith Baller-Gerold syndrome developing hematopoeticabnormalities, thus leading to the revised diagnosis ofFanconi anemia [Farrell et al., 1994; Rossbach et al.,1995], or abnormal chromosome breakage studies inpatients with presumed Baller-Gerold syndrome[Quarrell et al., 1998]. Preis et al. [1995] and Cohenand Toriello [1996] describe patients with probableRothmund-Thomson syndrome, who also had cranio-synostosis and radial hypoplasia. Lastly, overlap with

Fig. 6. The patient’s sister at age 15 years, showing facial asymmetry, proptosis, a prominent nose, maxillary hypoplasia with a short philtrum andan apparently posteriorly rotated right ear.

174 Gripp et al.

the VACTERL association [Rossbach et al., 1996] syn-drome was noted, and subsequently proven to be Fan-coni pancytopenia.

The wide phenotypic variability of what is consideredBaller-Gerold syndrome in combination with the nu-merous reports of overlap with other disorders and re-vised diagnoses has led several investigators to ques-tion whether Baller-Gerold syndrome is a distinct en-tity [Cohen and Torriello, 1996; Quarrell et al., 1998],and to suggest that it be diagnosed based on the narrowphenotype of the original reports by Baller [1950] andGerold [1959]. Quarrell et al. [1998] consider the casespresented by Ramos Fuentes et al. [1994] and Galeaand Tolmie [1990] to fit this narrower definition, andthey recommend extensive cytogenetic and hematologi-cal studies for newly identified cases. The patient re-ported by Arena and Carlin [1989] may also fit thesecriteria, as he does not have additional malformations.

While our patient had craniosynostosis and radialaplasia, without other organ system involvement, andthus qualified for the narrow diagnosis of Baller-Geroldsyndrome, the hallux valgus in combination with thecoronal synostosis led us to consider the possibility of aTWIST mutation. Mutations in the TWIST gene havebeen discovered in patients with Saethre-Chotzen syn-drome [Howard et al., 1997; El Ghouzzi et al., 1997;Rose and Malcolm, 1997; Paznekas et al., 1998]. Itsgene product is a transcription factor with a basic he-lix-loop-helix domain. The helix-loop-helix domain isinvolved in dimerization, the prerequisite for DNAbinding. All previously reported mutations [for reviewsee Paznekas et al., 1998] are located 58 to or within thehelix-loop-helix domain, thus preventing a functionalgene product from being formed. In contrast, the novelmutation identified in our patient is located 38 of thesecond helix domain. This nonsense mutation predictsa premature termination, leading to a gene productwith intact DNA binding and helix-loop-helix domains,but lacking the last 22 amino acids of the carboxy-terminus. One may speculate that this mutation affectseither mRNA stability or protein folding and therebyleads to haploinsuffiency.

After the mutation was identified in our index case,we reviewed the family history and examined availablerelatives. The facial asymmetry, prominent nose, highpalate and the hallux valgus observed in the father andthe older sister were consistent with a mild presenta-tion of Saethre-Chotzen syndrome. These relativeswere subsequently shown to carry the Glu181Stop mu-tation, while the clinically unaffected mother and sisterdo not carry the mutation. Thus the phenotype of Sae-thre-Chotzen syndrome segregates with this mutation.It is unclear if the aqueductal stenosis seen in the af-fected sister is related to the TWIST mutation. Whilerare cases of hydrocephalus due to aqueductal stenosisin combination with craniosynostosis have been noted[cases 1 and 2 in Fishman et al., 1971], and dilatationof the lateral ventricles was reported in one case ofSaethre-Chotzen syndrome [Bartsocas et al., 1970], nopatient with hydrocephalus due to aqueductal stenosishas to our knowledge been seen in the numerous largefamilies segregating Saethre-Chotzen syndrome. It ispossible that the aqueductal stenosis is unrelated to

the TWIST mutation, as the most common cause foracquired aqueductal stenosis in this age group is a tec-tal glioma [Barkovich and Newton, 1989], although amagnetic resonance imaging study did not show anyevidence of glioma in this patient.

Radial aplasia has to our knowledge not been seen inSaethre-Chotzen syndrome. One may speculate thatadditional cases of Baller-Gerold syndrome are due toTWIST mutations. The possibility of heterogeneity, in-cluding dominant inheritance pattern, has been raisedby other authors [Arena and Carlin, 1988; Galea andTolmie, 1990]. We found several previous reports thatcould be consistent with autosomal dominant inheri-tance; e.g., Temtamy and McKusick [1978] described apatient with coronal synostosis and bilateral radialaplasia. His sib was ‘‘found to have a peculiar skullshape,’’ and his mother had a ‘‘peculiar shape of herskull and a short upper lip, giving her a facial appear-ance suggesting the Crouzon syndrome.’’ The maternalgrandmother and maternal sibs reportedly had facialfindings similar to the mother’s [Temtamy and Mc Ku-sick, 1978]. Case 3 of Lin et al. [1993] was born to abrachycephalic father with a highly arched palate, whoreportedly had ‘no soft spots‘ as an infant. Lastly, onemay speculate if the affected sibs reported by Gerold[1959] may have been born to a parent carrying a dom-inant mutation. Unfortunately, the parents are onlycalled healthy and are not further described. The af-fected son was said to have epicanthus and small,poorly differentiated ears [Gerold, 1959], findings thatcould be consistent with a TWIST mutation. Futurestudies of additional cases with Baller-Gerold syn-drome will show what percentage are due to TWISTmutations.

In summary, we identified a novel TWIST mutationin a patient whose presentation was consistent withthe narrow definition of Baller-Gerold syndrome. Thislends further support to the hypothesis that Baller-Gerold syndrome is not a distinct entity, but shouldrather be considered a heterogeneous phenotype. Wehave now added a autosomal dominant disorder, Sae-thre-Chotzen syndrome, to the differential diagnosis ofthe Baller-Gerold phenotype; therefore, the evaluationof patients with this phenotype should include muta-tion analysis of the TWIST gene.

ACKNOWLEDGMENTS

We thank the patient and her family for their coop-eration. Karen W. Gripp is supported by the HowardHughes Medical Institute.

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